1. Field of the Invention
The present invention relates to a control device for a hybrid vehicle which is propelled by drive from an engine and a motor. In particular the invention relates to a control device for a hybrid vehicle for performing control of the driving force in the case where the output from the engine is rapidly increased from a situation where there is no assistance from the motor such as at the time of vehicle deceleration.
2. Description of the Related Art
Heretofore, there is known a hybrid vehicle incorporating a motor in addition to an engine as a drive source for vehicle propulsion. For one type of such hybrid vehicle, there is a parallel hybrid vehicle where the motor is used as an auxiliary drive source for assisting the output from the engine. With this parallel hybrid vehicle, for example, at the time of acceleration, the output from the engine is assisted by means of the motor, while at the time of deceleration, charging to a battery is performed by deceleration regeneration of the motor. Thus, with the parallel hybrid vehicle, various control is carried out, so that the residual capacity (electrical energy) of the battery can be maintained while satisfying the requirements of the driver. Such a parallel hybrid vehicle is disclosed, for example, in Japanese Patent Application, First Publication No. Hei 7-123509.
According to the control device for the abovementioned conventional hybrid vehicle, assistance (auxiliary drive) by the motor is provided during acceleration of the hybrid vehicle. However, in the case where, for example, after a condition where fuel supply to the engine has been stopped such as at the time of vehicle deceleration, fuel supply is suddenly reopened to move to acceleration, the driving force suddenly increases following the increase in output from the engine. Therefore, there is the problem of a sudden change occurring in the driving conditions of the hybrid vehicle. In order to address this problem, there is known a method where a sudden increase in driving force is suppressed by, for example, retarding the ignition timing of the engine, or by gradually increasing the throttle opening with the throttle actuator rather than following the movement of the throttle pedal, even in the case where the driver rapidly presses on the throttle pedal. However, with such a method where only the engine is controlled to suppress a rapid increase in the driving force, there is a problem of a deterioration in fuel consumption.